Predictions on atomic structures of Ti_1-xMo_xC using combined approach of first-principles calculation and the cluster expansion method

Recently, binary transition metal carbides such as (Ti_1-xMo _x)C have attracted much attention for use in increasing the strength of steels. This study aims to understand the ground state structure of various compositions of that carbide. Using a combined approach of first-principles calculation and the cluster expansion method, ground state structures of the compositions of TiC and MoC were determined. Only 29 symmetrically inequivalent structures were sufficient to determine the ground state structures of (Ti _1-xMo_x) C for the whole range of the composition. The linear chains of solute atoms predicted by calculation were favored when the compositions of MoC were between 20 at.% and 70 at.%. When the composition of MoC was 50 at.%, an alternating layer of Ti and Mo formed along the <111> direction. This layered structure is expected to show peculiar mechanical and electronic properties.